Fax machines became popular around the
world in the 1980s.
In order to reduce paper consumption we use
paperless fax machine.
In this paperless fax machine single-touch
panel is used as input and output device
Transmitted and received fax documents are
stored in memory.
A pressure sensitive stylus is used to write on
the touch panel.
Handwriting reconstruction algorithm is used.
The modem module for sending and receiving faxes.
The touch panel displays the fax documents and
accepts the handwriting signatures.
The tip of the pressure sensitive stylus is connected to
a pressure sensor through a spring coil.
During a signing act, the pressure at the tip is
measured, digitalized by an ADC, and finally sent to
MCU for subsequent processing.
The touch panel fax machine can operate in one of
the three modes:
1. Fax receiving mode
2. Browsing and handwriting mode
3. Fax transmitting mode
The handwriting reconstruction algorithm,
turn an user’s signing act into a digital
signature as close to the original as possible.
During the signing act, the data from the
pressure sensitive stylus and the touch panel
are sampled by using timer interrupts in MCU
analog values are
then converted into
digital values by ADCs
and buffered in two
FIFO queues in order
as shown in figure.
Some issues that are considered in data
collection and processing.
1. Resolution of touch panel
2. Signal synchronization
3. Pressure and Strokes
4. Handwriting Reconstruction
Resolution of touch panels:
A single-touch panel is composed of two major parts,
an LCD screen for displaying and a thin touch layer for
The resolution of an LCD screen is specified explicitly by
enumerating the number of pixels both in width and
The resolution of the touch panel is determined by the
number of bits used in the ADCs adopted
Single-touch panels can response exact one location
that is being touched at a time.
Timer interrupt intervals are made set to be constant.
According to changes in the pressure data measured,
handwriting reconstruction algorithm can generate the
strokes with different thickness.
A simple two-step calibration
procedure for the stylus is
performed before writing.
First, press the pen tip all the
way down and record the
pressure reading as PF .
Next, let the tip off the touch
panel and record the pressure
again as PE.
For any pressure P, the
pressure ratio(PR) is calculated
There are two types of methods to generate
thickness of the stroke
1. line extension
2. circular extension
Circular extension is used in handwriting
By using handwriting reconstruction algorithm
the signature can be exactly reproduced.
Consumption of paper can be reduced.
• ITU-T.37: Procedures for the Transfer of
Facsimile Data via Store-and forward on the
• ITU-T.38: Procedures for Real-time Group 3
Facsimile Communication over IP Networks,
Amendment 1, 1999.
• Handwriting Recognition Group,
<hwr.nici.kun.nl>, May, 2008.